Extreme is more like La Paz Bolivia @ amout 14k feet. I understand approach/land procedure is oxy on. They have oxygen standing by in the airport I am told.
Only problem I ever has was out of Quito about 9.3k, for some reason auto-press did not kick in after T/O and we had to go manual, we had masks on and were at 14k cabin by the time we got the environment under control.
As P.A. said dial it in. In any aircraft with auto pressurization it only becomes a big deal if a system fails or the landing alt is dialed in incorrectly. E.G. had a new F/E who dialed in 2k feet for 200 feet. I thought the entry door was broken at the gate, tried the other side (stuck as well) and figured it out.
This has the potential to be dangerous. Most aircraft are not supposed to land with more than 1psi D.P. on the hull for structural reasons I suppose.